The present invention relates to an oil pump mounting system for internal combustion engines, and that is capable of ensuring operation even when the engine is inclined.
As is well known to those skilled in the art, an oil pump mounting system of the type disclosed in, for instance, Japanese Utility Model Publication No. 56-27367 or Japanese Utility Model Laid-Open Publication No. 60-70703 is incorporated in a vertical shaft type engine mounted on a lawn mower or the like.
In the case of the oil pump mounting system of the type described above, an oil pump is mounted in an oil pan through a mount hole formed through one wall thereof and the mount hole is then closed with a cover with bolts and nuts or any other suitable joint means. As the engine is started, the oil pump is rotated so that oil stored in the oil pan is distributed to various parts for lubrication.
However, in the case of the oil pump mounting system of the type described above, due to vibrations caused by the operation of the engine, the bolts are loosened so that there is a fear that the oil stored in the oil pan leaks.
In order to solve this problem, there has been devised and demonstrated an oil pump mounting system as shown in FIG. 5.
That is, an oil pan 1 is formed integrally with a pump housing 2, and a bearing 5 for supporting an output shaft 4 of an engine 3 is securely mounted on the top of the pump housing 2. A space defined by the bearing 5 and the pump housing 2 is used as a rotor chamber 7 in which an oil pump 6 is housed.
When the engine 3 is started, the output shaft 4 is rotated so that a driving shaft 8 of the oil pump 6 joined to the output shaft 4 with a pin 4a is rotated. Therefore, the oil within the oil pan 1 flows through a suction port 9 defined between the top of the pump housing 2 and the bearing 5 to the top of the rotor chamber 7 and then is increased in pressure by the oil pump 6 and distributed to rotating parts of the engine 3 through an oil passage 4b extending through the output shaft 4.
In the conventional oil pump mounting system of the type just described above, however, since the suction port 9 is defined between the top of the pump housing 2 and the bearing 5, an opening 9a of the suction port 9 is exposed above the level of the oil when the engine 3 is inclined so that the flow of the oil into the pump housing is adversely affected. In order to solve this problem, a relatively large quantity of oil must be stored in the oil pan 1 and it is difficult to mount the engine 3 at a position below a predetermined height.
Furthermore, one end of the driving shaft 8 of the oil pump 6 is joined with the pin 4a to the output shaft 4 of the engine 3 so that, when the engine 3 is inclined, the driving shaft 8 is also inclined to adversely affect so that the smooth and reliable operation of the oil pump 6 can be attained.